How to test your RAM for errors
It you purchase new ram, a new or used computer or experience crashes and bluescreens you should definitely test the memory installed on your computer to make sure that it is running without errors. Faulty memory is one of the main reasons for instability. The first task should be to make sure that the memory is correctly inserted into the memory banks. Make sure you count the number of bars and check if you are running dual channel mode or not.
If you are not sure what all of this means, consult the manual that shipped with your motherboard. If you purchased a PC instead, you may find the manual in electronic form on the hard drive. If not, contact the manufacturer of the PC to find out more about it.
Download the free software Memtest86+ as an iso image (currently Memtest 3.3 iso) and burn it to a CD or DVD. In many newer versions of Windows, you can simply right-click the ISO and select the burn to disc option that should be displayed here. If that is not the case, try a program like ImgBurn instead which you can do the burning with.
Reboot your computer afterwards and boot the CD that you just created. You might need to change the boot order in your bios to be able to boot from CD. Memtest86+ is starting automatically from CD and performing in depth memory tests that could take hours to complete.
If errors are encountered during the test you know that you have faulty RAM and need to replace it. If you have more than one RAM bar installed you should test them separately to make sure you know which one is the faulty one. I ran the test just a few hours ago and realized that one of my ram bars is indeed faulty which made me order new RAM immediately.